Humans come in different sizes and colours. Skin colour comes from a pigment called #melanin, produced by skin cells called #melanocytes.Most of us, pale or dark, prefer to have evenly pigmented skin.
People suffering from #vitiligo have patchy skin, with pale areas that are deficient in melanin and other areas with normal pigmentation (see picture). It is apparently an autoimmune condition, where the immune system attacks the body’s own melanocytes.
Although pale skin patches may be more prone to sunburn, vitiligo does not have serious medical consequences, though sufferersmay experience embarrassment and lack of confidence. Some may use cosmetics to darken and hide blotches. Others may try controlled exposure to sun or UV lamps to tan their skin.
An interesting treatment for vitiligo is #PUVA,a photodynamic therapy, where the patient is administered a “photosensitizer” molecule and then exposed to UVA radiation (Barros et al, 2021).
The photosensitiser molecules absorb the light and use the energy to activate oxygen (#ROS) that stimulates skin cells to synthesise more melanin. The mechanism is similar to normal sun-tanning, but PUVA gives higherstimulation with less UV damage. Besides vitiligo, PUVA is also used to treat psoriasis and other skin disorders.
The PUVA photosensitiser is #Methoxsalen(molecule in picture), a linear furanocoumarin or “psoralen” discovered firstin the plant Ammi majus (Apiaceae).This plant had already been used for vitiligo treatment in the Arab world hundreds of years earlier (attributed to Ibn al-Baytar, https://hdl.loc.gov/loc.wdl/wdl.7466).Plants in the Apiaceae include carrots, celery, parsley, Angelica, caraway, etc. Many of these are medicinal species, and some contain significant amounts of psoralens. Though useful in PUVA, psoralens are double-edged swords as they can also cause nasty #phytophotodermatitis (e.g. see Klaber, 2006).
Now let’s mention the social malady colour prejudice, about which JH Griffin wrote the book “Black Like Me” (1961) documenting his experiences in the southern USA. He used Methoxsalen to darken his skin for the project.
References
🖝 Barros NM et al (2021). Phototherapy. Anais brasileiros de dermatologia, 96(4), 397–407. https://doi.org/10.1016/j.abd.2021.03.001
👉 Klaber R. E. (2006).Phytohotodermatitis. Archives of disease in childhood, 91(5),385. https://doi.org/10.1136/adc.2005.091934
🖝 Wikipedia (2024) Black Like Me. https://en.wikipedia.org/w/index.php?title=Black_Like_Me&oldid=1216523820
